Landing with Nasty Gusts
In the AOPA Pilot article “Maintain Thy Groundspeed,” Barry Schiff analyzes in detail what can go wrong when wind shear is encountered on short final approach.
Of course, there is the traditional formula to prevent mishaps: Airspeed is increased by half of the gust factor. But how large is the gust factor? If an ASOS station is based at the airport, it provides that information about gusts. But even that supposedly timely information can prove to be quite wrong when a huge gust randomly occurs. Instead, Barry Schiff recommends that the pilot maintain groundspeed equal to normal approach speed, and argues that this suffices regardless of the speed of the gusts.
Recently, we had several opportunities to try out the rule. A particularly nasty case of gusts occurred at Aero Country Airport, the final destination after a trip to New Mexico and back. Winds were given as 20 kts gusting to 29 by a message broadcast from the nearby McKinney Airport. The information is updated every hour and thus may be quite wrong. Trees to the east of the Aero Country runway were bending and shaking in fierce gusts. How could anybody be sure that the gust factor was just 9 kts?
We used the groundspeed equal to normal approach speed rule, which is easily implemented using GPS. It took a modest amount of power to maintain that speed during the descent on short final. As we crossed the threshold and then came into ground effect over the runway, we pulled power all the way back. Low over the runway, the airspeed bled off rapidly as we focused on counteracting the strong gusts of the turbulent air. Not to worry, though. If the plane stalled, it would just drop two feet or so, a not so nice but manageable event. As we slowly raised the nose, the mains touched down gently, and finally the nose wheel descended onto the runway. Due to the headwind, groundspeed at that point was very low, and the rollout was short.
A short time later, a Piper Cub came in for landing. Evidently, the pilot was surprised by a particularly large gust since the engine went to full power just 300 ft away from the threshold. The sudden downdraft almost forced the plane onto the ground short of the runway.
No doubt, the rule works very well for us, and we will use it from now on in gusty wind conditions. Thank you, Barry Schiff, for pointing it out in a lucid and convincing article.
Of course, there is the traditional formula to prevent mishaps: Airspeed is increased by half of the gust factor. But how large is the gust factor? If an ASOS station is based at the airport, it provides that information about gusts. But even that supposedly timely information can prove to be quite wrong when a huge gust randomly occurs. Instead, Barry Schiff recommends that the pilot maintain groundspeed equal to normal approach speed, and argues that this suffices regardless of the speed of the gusts.
Recently, we had several opportunities to try out the rule. A particularly nasty case of gusts occurred at Aero Country Airport, the final destination after a trip to New Mexico and back. Winds were given as 20 kts gusting to 29 by a message broadcast from the nearby McKinney Airport. The information is updated every hour and thus may be quite wrong. Trees to the east of the Aero Country runway were bending and shaking in fierce gusts. How could anybody be sure that the gust factor was just 9 kts?
We used the groundspeed equal to normal approach speed rule, which is easily implemented using GPS. It took a modest amount of power to maintain that speed during the descent on short final. As we crossed the threshold and then came into ground effect over the runway, we pulled power all the way back. Low over the runway, the airspeed bled off rapidly as we focused on counteracting the strong gusts of the turbulent air. Not to worry, though. If the plane stalled, it would just drop two feet or so, a not so nice but manageable event. As we slowly raised the nose, the mains touched down gently, and finally the nose wheel descended onto the runway. Due to the headwind, groundspeed at that point was very low, and the rollout was short.
A short time later, a Piper Cub came in for landing. Evidently, the pilot was surprised by a particularly large gust since the engine went to full power just 300 ft away from the threshold. The sudden downdraft almost forced the plane onto the ground short of the runway.
No doubt, the rule works very well for us, and we will use it from now on in gusty wind conditions. Thank you, Barry Schiff, for pointing it out in a lucid and convincing article.
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